Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

217
FXUS63 KLOT 021909
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
209 PM CDT Sat May 2 2026

.KEY MESSAGES...

- Period of rain showers Sunday morning, followed by mostly
  dry conditions for the afternoon.

- Additional period of showers and thunderstorms (30-50%
  chance) late Monday into Tuesday. A few storms could become
  strong to severe (mainly south of I-80) Monday evening.

- Outside of a brief warmup Sunday into Monday, near to below
  normal temperatures are favored through next weekend with
  occasional chances for rain showers.

&&

.DISCUSSION...
Issued at 209 PM CDT Sat May 2 2026

Subtle mid-level ridging continues to reside across the Midwest
and western Great Lakes this afternoon which will keep tranquil
weather conditions in play through tonight. Despite the
widespread diurnal cumulus, temperatures have continued to warm
into the lower to mid- 50s and there is a chance that some
locations could even attempt to tag 60 (mainly near and west of
I-39) before sunset. As the diurnal cumulus erode this evening,
temperatures should cool into the upper 30s to lower 40s before
additional cloud cover returns after midnight. Given the
increasing cloud cover overnight and the slightly elevated
winds, conditions do not look overly favorable for widespread
frost tonight. However, some localized pockets of patchy frost
may still develop especially across northwest IN.

Heading into Sunday, the shortwave trough that is currently
near the ND-Canadian border will be pivoting into northern IL.
As it does so it will be interacting with a plume of mid-level
moisture which should lead to the development of scattered
showers across northern IL and eventually northwest IN. Since
the wave is expected to be rather progressive, the rain showers
should only last 2-3 hours at any one location and should fully
exit our forecast area by early afternoon. In the wake of the
shortwave, modest subsidence and a plume of drier air aloft
should keep the atmosphere capped to any additional shower
development Sunday afternoon. However, there will be a weak
surface convergence boundary stretching from northeast OH to
eastern MO Sunday afternoon which may allow for some isolated
showers or storms to develop near this boundary and drift into
our far southern CWA during the late afternoon and evening
hours. With the aforementioned capping and the boundary forecast
to be south of our area have opted to keep some silent (10-14%)
POPs near and south of US-24 just in case but suspect we should
stay dry.

Otherwise, Sunday will feature more typical early May
temperatures in the mid to upper 60s courtesy of stout
southwesterly winds. That said, expect wind gusts Sunday
afternoon to peak around 30-35 mph despite the partly to mostly
cloudy skies. Gusts will taper Sunday evening as skies clear and
the atmosphere decouples. Though the continued warm advection
will keep temperatures mild in the mid-40s.

A secondary and more amplified shortwave trough will be digging
out of Canada towards the Great Lakes on Monday which in turn
will push a cold front southward towards and eventually through
northern IL and northwest IN. Guidance has come into better
agreement that the cold front should remain north of our area
until late Monday afternoon and evening which means that most of
the daytime hours should be dry. Additionally, the prevailing
southwesterly breezes look to allow temperatures to top out in
the mid-70s Monday afternoon. Though, once the cold front
arrives it will bring with it widespread showers and
thunderstorms. Forecast soundings ahead of the front continue to
show that low-level moisture may be limiting factor (dew points
forecast to be in the lower to mid-50s) which could limit the
coverage of thunderstorms especially for the northern half of
our area. That said, there will be sufficient instability to at
least support some storms Monday afternoon and evening and given
that there will be around 35-40 kts of deep layer shear
present, a few storms could even become strong to severe. While
the Storm Prediction Center does have a marginal (level 1 of 5)
risk for severe storms Monday evening for areas south of I-80,
the aforementioned limited moisture does make this threat low
confidence. Regardless, if any strong to severe storms do
materialize the main threats look to be gusty winds and
instances of hail.

The cold front and its associated showers will progress into
central IL and IN Monday night into Tuesday, but will begin to
stall as it does so. This stalling boundary in addition to the
continued forcing from the shortwave trough over the Midwest
(that may even attempt to phase with a southern CA shortwave)
should keep showers and isolated storms ongoing through much of
the day on Tuesday. With the better instability expected to be
south of our area into central IL and IN the threat for severe
weather looks very low on Tuesday. However, shower/storm motions
will be parallel to the aforementioned stalled frontal boundary
and look to support training convection which is expected to
result in a period of soaking rainfall especially across our
southern CWA. Since the anticipated rain amounts of 1.0-1.5
inches are expected to fall over the course of 24-36 hours, the
threat for flash flooding does look to be low. Though, the
rainfall may still lead to river rises and localized ponding
issues in lower- lying areas.

The widespread rain is forecast to start tapering Tuesday night
into Wednesday as the shortwave pivots into the eastern Great
Lakes and the front drifts into the Ohio River Valley. While
this should give us a reprieve for Wednesday, another shortwave
is progged to pivot into the Great Lakes Wednesday night into
Thursday which should allow for additional rain showers to
develop. With the frontal zone expected to be stalled near the
Ohio and Tennessee River Valleys the better coverage of showers
(and thunderstorms) should focus to our south, but cannot fully
rule out some glancing showers in our southern CWA on Thursday.
Regardless, broad troughing is expected to return to the Great
Lakes next week which will keep temperatures near to below
average with daily highs in the 50s to near 60 and overnight
lows in the 30s and 40s Tuesday onward. This pattern will also
support occasional rain chances into next weekend as shortwaves
pivot through the pattern, but details on exactly when and where
these waves will go remain uncertain at this range.

Yack

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 1221 PM CDT Sat May 2 2026

Key Messages:

- Lake breeze likely not to impact the main Chicago terminals
  this afternoon.

- Brief period of scattered showers possible Sunday morning.

- Increasingly gusty southwest winds on Sunday.

A lake breeze boundary has developed again near the lake early
this afternoon. While it will attempt to move inland across
northeastern IL this afternoon, westerly surface winds farther
inland are expected to remain just strong enough to keep it
east of ORD and MDW through the day. Accordingly, unlike the
past couple of afternoons, we do not anticipate an easterly wind
shift at the ORD or MDW today. Expect the winds to turn light
from the southwest this evening and tonight, then ramp up and
becoming increasingly gusty on Sunday as the surface gradient
strengthens in advance of an approaching surface frontal
trough. The strongest southwesterly wind gusts are expected to
be up to ~30 kt from midday into the afternoon.

A quick moving weather impulse is also expected to track across
the area Sunday morning. As it does, a brief period of rain
showers could materialize across portions of the area Sunday
morning. We thus continue to highlight this potential with a
PROB30 from 14 to 17 Z Sunday. Otherwise, VFR conditions are
anticipated through the period.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 7 AM to 7 PM CDT Sunday for the IL
     and IN nearshore waters.

&&

$$

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